JP4888833B2 - High pressure discharge lamp lighting device - Google Patents

Description

  The present invention relates to a technique for preventing heating of a high pressure discharge lamp lighting device due to a decrease in lamp voltage in a high pressure discharge lamp lighting device having an improved life of the high pressure discharge lamp.

  In recent years, high pressure discharge lamp lighting devices having a circuit configuration shown in FIG. 1 are becoming widespread in projectors using a high pressure discharge lamp. This high pressure discharge lamp lighting device comprises a DC power source 1, a step-down chopper circuit 2, a full bridge circuit 3, an igniter circuit 4, a dimming control circuit 9 and a control circuit 10, and the igniter circuit 4 includes an igniter control circuit 7 and is controlled. The circuit 10 includes a PWM control circuit 5 and a full bridge control circuit 6.

The DC power source 1 only needs to rectify and smooth a commercial AC power source, and generally includes a power factor correction circuit and the like. Further, the lighting circuit detects a voltage of the high pressure discharge lamp La (hereinafter referred to as “lamp voltage”), a voltage detection circuit including resistors R1 and R2, and a current flowing through the high pressure discharge lamp La (hereinafter referred to as “lamp current”). And a current detection circuit including a resistor R3.
The PWM control circuit 5 converts the output current of the DC power supply 1 to an appropriate value by controlling the ON width of the switching element Q1 of the step-down chopper circuit 2, and then the output current is output to the full bridge circuit 3.

The full bridge control circuit 6 alternately turns on the switching elements Q2 and Q5 and Q3 and Q4 of the full bridge circuit 3, and immediately before the half cycle of the low frequency rectangular wave current as shown in FIG. The lamp current applied with one cycle of current is output to the high-pressure discharge lamp La.
That is, the current value of the AC lamp current is controlled by the PWM control circuit 5, the time width between the polarity inversions is controlled by the full bridge control circuit 6, and they operate in cooperation within the control circuit 10. In FIG. 2A, the peak current value in the second half of the high frequency period is 1.1 to 1.5 times the current value in the low frequency period, and the time width of one cycle in the high frequency period is low. The time width of the half cycle of the frequency period is 1: 4 to 1:20. Further, it is a diagram showing the lamp voltage fluctuation in the life at the time of all light and dimming in the conventional example {1 high frequency cycle + low frequency half cycle (negative) + 1 high frequency cycle + low frequency half cycle (positive)} 1 The cycle is about 60 Hz to 1 kHz.

  Here, the current example in FIG. 2 (a) is a half cycle low frequency current duration: 2.5 mSec, a high frequency current first half duration: 0.25 mSec, a high frequency current second half duration: It is set to 0.25 mSec.

  The igniter control circuit 7 applies a voltage of several hundred volts to the primary winding N1 of the transformer T1 before starting the high-pressure discharge lamp La, thereby applying a high voltage pulse (several kV to several kV) to the secondary winding N2. Several kV) is generated, and the high-pressure discharge lamp La is started. After starting the high-pressure discharge lamp La, the igniter control circuit 7 stops its operation.

  The dimming control circuit 9 receives the dimming signal from the outside of the lighting device (the dimming signal oscillation circuit 8), and the PWM control circuit 5 controls the transistor Q1 of the step-down chopper circuit 2 so that the set dimming power is obtained. By controlling (decreasing) the on-duty, the power of the high-pressure discharge lamp La (hereinafter referred to as “lamp power”) is reduced.

  The cooling fan control unit 11a increases or decreases the output of the cooling fan 11b according to the dimming signal as will be described later. The cooling fan control unit 11a and the cooling fan 11b are not included in the high pressure discharge lamp lighting device.

FIG. 4 shows, for example, lamp power characteristics of total optical power 180 W and dimming power 140 W as an example. In FIG. 4, the horizontal axis represents the lamp voltage and the vertical axis represents the lamp power, which shows the power characteristics during all-light lighting and the power characteristics during dimming.
In the example of FIG. 4, constant current control of 3 A is performed until the lamp power reaches the set total light power and the set dimming power. In the 180 W all light mode, the lamp voltage is determined from 60 V (V _t-full ) or more. In the case of power control and a 140 W dimming mode, constant power control is performed from a lamp voltage of 47 V (V _t-dim ) or more.

By the way, when the high pressure discharge lamp is turned on, the following two points must be considered for the lamp current waveform to be input.
The first point is prevention of flicker. The flicker referred to here is a phenomenon in which the starting point of the discharge arc moves on the electrode while the high pressure discharge lamp is lit, and the light output flickers. The phenomenon that the electrode grows in a protruding shape is not necessarily clear, but is estimated as follows. When the heated tungsten is evaporated, it is combined with halogen or the like present in the arc tube to form a tungsten compound.
This tungsten compound diffuses from the vicinity of the tube wall to the vicinity of the electrode tip by convection or the like, and is decomposed into tungsten atoms at a high temperature portion. Tungsten atoms become cations when ionized in the arc. Both electrodes that are lit with alternating current repeat the anode and cathode at each lighting frequency, but when this cathode is operating, the cations in the arc are attracted to the cathode side by the electric field, and are deposited at the tips of both electrodes. It is believed that it forms a protrusion.

  To solve this problem, a lamp current waveform as shown in FIG. 2 (a) is used to form a protrusion of an appropriate size at the tip of the electrode by the action of the latter half cycle of the high-frequency current, and the arc is formed on the protrusion. It has been found that flicker can be suitably prevented by determining the starting point (for example, Patent Document 1).

  The second point is maintaining a proper lamp voltage. That is, it is necessary to appropriately suppress the growth of the protrusions formed on the electrodes so that the distance between the electrodes is maintained in an appropriate range. The protrusions need to be present to prevent flicker, but as long as the starting point of the arc is determined, it is not necessary to be longer.

Here, FIG. 5 shows changes in the lighting time and lamp voltage in the life of the lamp.
As can be seen from FIG. 5, the lamp voltage temporarily drops due to the initial growth of the protrusions at the tip of the electrode.
Furthermore, when dimming, the electrode temperature is lower and tungsten evaporation is less than when all light is lit, so the protrusions grow more easily than when all light is lit. As a result, the lamp voltage is higher than when all light is lit. The initial decline of the becomes larger.

  Regarding this decrease in lamp voltage, for example, in Japanese Patent Application No. 2006-217807, for a normal rectangular wave lighting high pressure discharge lamp lighting device, when the detected lamp voltage is less than the set lamp in a predetermined period after the lamp lighting starts. In the case where the protrusion has grown too much, a large lamp current is applied to suppress the growth of the protrusion so that the distance between the electrodes is not further reduced.

On the other hand, in recent years, in projectors using high-pressure discharge lamps, reduction of cooling fan noise during operation has become an important issue. For this reason, in general, when dimming lighting is used for all-light lighting, lamp power is reduced at the same lamp voltage, and the amount of heat generated by both the high-pressure discharge lamp lighting device and the lamp is reduced. In order to reduce the operating voltage (that is, output) of the cooling fan 11b, it has been studied to reduce the noise.
JP 2001-244088 A

However, it cannot be generally said that the circuit loss of the high pressure discharge lamp lighting device is sufficiently small compared to the loss during dimming. As shown in FIG. 6, when the lamp voltage is about 60V or more, the circuit loss (dotted line) at the time of dimming lighting is correspondingly smaller than the circuit loss (solid line) at the time of all light lighting, but the lamp voltage is 60V. The difference in circuit loss is reduced from near (V _t-full ) to around 47 V (V _t-dim ), and the difference disappears when the lamp voltage is around 47 V. Therefore, at the time of dimming, the output of the cooling fan is lowered even though the circuit loss is not significantly different from that at the time of all light. In particular, in the vicinity of a lamp voltage of 47 V, there is a state where the circuit is sufficiently cooled during all light and not sufficiently cooled during dimming although the circuit loss is the same.

  Therefore, to reduce the noise of the cooling fan during projector operation, if the operating voltage of the cooling fan is lowered during dimming lighting, the high pressure discharge lamp lighting device will generate heat when the lamp voltage during dimming lighting in the early lamp life decreases. There is a possibility of reaching the operating temperature of the temperature protection circuit without being able to cool, and in the worst case, it may cause destruction of the high pressure discharge lamp lighting device.

  In addition, regarding this lamp voltage drop, for example, in the above-mentioned document (Japanese Patent Application No. 2006-217807), in a normal rectangular wave lighting high-pressure discharge lamp lighting device, When the voltage is lower than the set lamp voltage (when the protrusions grow too much), the lamp current is increased to suppress the growth of the protrusions so that the distance between the electrodes does not decrease further. Also in this case, since the current supplied from the high pressure discharge lamp lighting device is increased until the lamp voltage is recovered, heat generation of the high pressure discharge lamp lighting device is increased, which is not a fundamental measure.

  Therefore, while considering the prevention of flicker due to the formation of protrusions even at the time of dimming, it does not increase the heat generation of the high pressure discharge lamp lighting device, and prevents the lamp voltage from decreasing due to overgrowth of the protrusions (or recovers the reduced lamp voltage). )is required.

A first aspect of the present invention is a high-pressure discharge lamp lighting device used in a light source device having a cooling fan whose output is reduced during dimming, wherein the cooling fan cools the inside of the light source device. A power supply circuit for supplying an alternating current to the high-pressure discharge lamp, a control circuit for periodically changing the current value of the alternating current supplied by the power supply circuit and the time width between polarity inversions, and receiving from the outside The dimming control circuit reduces the power to the set power based on the dimming signal, and the AC current has a predetermined frequency immediately before a half cycle of a rectangular wave current (hereinafter referred to as “low frequency current”) having a predetermined frequency. Higher frequency current (hereinafter referred to as “high-frequency current”) consists of repetition of a current waveform applied for one cycle, and only the latter half cycle or one cycle of one cycle of the high-frequency current. In the high pressure discharge lamp lighting device in which the power supply circuit is controlled by the control circuit so that the peak current value of all the peaks is higher than the current value of the low frequency current, the control circuit includes a detection circuit for detecting the high pressure discharge lamp voltage. , tone if the high-pressure discharge lamp voltage falls below a predetermined set value V _s at the time of light, a high pressure discharge lamp lighting device configured to extend the duration of the half cycle of the low frequency current.

Here, when the duration of the half cycle of the low frequency current is lengthened, {one high frequency cycle + low frequency half cycle (negative) + high frequency one cycle + low frequency half cycle (positive)} is one cycle in the control circuit. Then, the period was set to 60 Hz to 100 Hz.
In the control circuit, release pressure when the high pressure discharge lamp voltage if that maintains more than a predetermined value V _t that is controlled to power supplied to the high pressure discharge lamp is constant, lower than a predetermined value V _t The electric current supplied to the electric lamp is controlled to be constant, and the predetermined set value V _s is made equal to the predetermined value V _t-full for all-light lighting.

  According to a second aspect of the present invention, there is provided a high pressure discharge lamp lighting device according to the first aspect, a dimming signal oscillation means for generating a dimming signal, a cooling fan, a high pressure discharge lamp, a reflector to which the high pressure discharge lamp is attached, and at least It is a light source device comprising a housing containing a high pressure discharge lamp lighting device.

  According to the high pressure discharge lamp lighting device and the high pressure discharge lamp lighting method of the present invention, when the lamp voltage is lower than the predetermined voltage, the duration of the low frequency current in each half cycle is made longer than before, and one cycle of the high frequency is performed. + Low frequency half cycle (negative) + High frequency 1 cycle + Low frequency half cycle (positive) is 1 cycle. By setting the cycle to 60Hz to 100Hz, heat generation during dimming of the high pressure discharge lamp lighting device is increased. In addition, it is possible to suppress an excessive lamp voltage drop while increasing the electrode temperature during the anode operation and preventing flicker.

Embodiments of the present invention will be described below.
The circuit configuration is the same as that shown in FIG. 1, and the description of the configuration and operation is omitted. The difference between the present invention and the conventional example is the duration of the low-frequency current in each cycle when the lamp voltage falls below the set lamp voltage. In the present invention, when the lamp voltage becomes lower than the set value V _s , in order to increase the electrode temperature rise on the anode operating side and keep the temperature difference in the arc spot portion optimal, The duration of the low frequency current is set to 5 mSec or more.

Here, the present invention will be described in a dimming lighting mode in which the initial lamp voltage is greatly reduced. For example, when considering a slight initial lamp voltage reduction in the all-light lighting mode, the lamp is a constant power lamp voltage in the all-light lighting mode. Assuming that the lower limit value of the range is 60V, the initial set value of the lamp voltage has a lower limit of 65V, for example, with a margin of 5V.
When a lamp with this lower limit lamp voltage is used for dimming lighting, the lamp power is lower and the electrode temperature is lower than that for all-light lighting. Therefore, the amount of tungsten evaporation is reduced, and the lamp voltage gradually decreases as protrusion growth is promoted. I will do it.

For example, when the set value V _s of the present invention and 60V, when the lamp voltage is decreased to 60V, switching the lamp current waveform from the waveform shown in FIG. 2 (a) to the waveform shown in FIG. 2 (b). The lamp current waveform in FIG. 2A is as follows: the duration of the low frequency current of the half cycle: 2.5 mSec, the duration of the first half of the high frequency current: 0.25 mSec, the duration of the second half of the high frequency current: 0 2b, the lamp current waveform of FIG. 2 (b) shows the half-cycle low-frequency current duration: 5.5 mSec, the high-frequency current first half-end duration: 0.25 mSec, the second half-high-frequency current half-end. Duration: 0.25 mSec.

  Then, since the lighting time of the low frequency part becomes longer, the electrode temperature on the side where both electrodes are anodic operates becomes higher, and the amount of tungsten evaporation increases compared to before, and the protrusion grows more than necessary. Is prevented.

Also, simply increasing the lighting time of the low frequency portion does not increase the supply current from the high pressure discharge lamp lighting device, and the circuit loss of the high pressure discharge lamp lighting device does not increase, so that heat generation increases at that time. There is nothing.
Furthermore, even if the lighting time of the low frequency part is lengthened, the current value of the latter half of the high frequency current immediately before that is 1.1 to 1.5 times the low frequency current, so the arc spot is fixed and flicker is suppressed. There is no cause.

Further, regarding the set value V _s , when the set value when the lamp voltage decreases is V _s1 , and the set value when the lamp voltage increases is V _s2 , V _s1 <V _s2 and the vicinity of the set value Therefore, frequent switching of the current duration of the low frequency half cycle is avoided.

  Further, when the lamp voltage becomes lower than the set value, the maximum value of the duration of the low frequency half cycle is limited, and {high frequency 1 cycle + low frequency half cycle (negative) + high frequency 1 cycle + low frequency half cycle ( (Correct)} is one cycle, it is desirable that the period be 60 Hz to 100 Hz. This is because if the duration of the low-frequency half cycle is further shortened (higher than 100 Hz), the electrode temperature during anode operation cannot be increased, and the above-described effect of the present invention becomes difficult to obtain. Further, if it is made longer (lower than 60 Hz), the electrode temperature at the time of anode operation becomes too high and damages the electrode, resulting in a rapid increase in lamp voltage and a shortened lamp life. Of course, even if the above-mentioned one cycle is less than 60 Hz, the minimum object of the present invention to avoid the failure of the high-pressure discharge lamp lighting device while suppressing noise by suppressing the output of the cooling fan during dimming can be achieved. .

  FIG. 3 shows an embodiment in which the present invention is applied to a light source device such as a projector. 61 is a high pressure discharge lamp lighting device of each embodiment described above, 62 is a reflector to which the high pressure discharge lamp La is attached, and 63 is a housing containing the high pressure discharge lamp lighting device 61, the high pressure discharge lamp La and the reflector 62. . In addition, the figure is a schematic illustration of the embodiment, and the dimensions, arrangement, and the like are not as illustrated. Then, a projector is configured by appropriately arranging video system members (not shown) in the housing 63. In addition, 8 is the above-mentioned dimming signal oscillation circuit, 9 is a dimming control circuit, 11a is a cooling fan controller, and 11b is a cooling fan. These connections may be wired or wireless. Although not shown, it is assumed that power is supplied to each component as appropriate.

  As described above, since the high pressure discharge lamp lighting device that generates less heat during dimming is built in, the reliability of the high pressure discharge lamp lighting device is ensured even if the fan output is reduced to reduce noise during dimming. . Therefore, a low noise and highly reliable light source device can be obtained.

  The present invention can be applied to optical applications such as projectors.

It is a figure which shows the circuit structure of a high pressure discharge lamp lighting device. It is a figure which shows the lamp current waveform of this invention (horizontal axis: time, vertical axis: current). It is a figure which shows the light source device containing a high pressure discharge lamp lighting device. It is a figure which shows the electric power characteristic at the time of all the lights and light control of a prior art example. It is a figure which shows the lamp voltage fluctuation | variation in the life at the time of all the lights and light control of a prior art example. It is a figure which shows the power characteristic and circuit loss at the time of all the light of the conventional example, and light control. It is a figure which shows the lamp voltage fluctuation | variation in the life at the time of all the lights and light control of a prior art example.

Explanation of symbols

1. 1. DC power supply 2. Step-down chopper circuit 3. Full bridge circuit 4. Igniter circuit PWM control circuit 6. 6. Full bridge control circuit 7. Igniter control circuit 8. Dimming signal transmission circuit Dimming control circuit 10. Control circuit 11a. Cooling fan controller 11b. Cooling fan La. High pressure discharge lamps R1, R2, R3. resistance

Claims (3)

A high pressure discharge lamp lighting device used in a light source device having a cooling fan whose output is reduced during dimming, wherein the cooling fan is for cooling the inside of the light source device. Based on a power supply circuit for supplying an alternating current, a control circuit for periodically changing a current value of the alternating current supplied by the power supply circuit and a time width between polarity inversions, and a dimming signal received from the outside The dimming control circuit reduces the power to the preset power, and the alternating current has a frequency higher than the predetermined frequency immediately before a half cycle of a rectangular wave current having a predetermined frequency (hereinafter referred to as “low frequency current”). Current (hereinafter referred to as “high-frequency current”) is a repetition of a current waveform applied for one cycle, and only the latter half cycle of one cycle of the high-frequency current or the entire one cycle In the high pressure discharge lamp lighting device said power supply circuit is controlled by the control circuit so that over leak current value becomes higher than the current value of the low frequency current,
Comprising a detection circuit for the control circuit detects a high pressure discharge lamp voltage, adjusted if the high-pressure discharge lamp voltage during light falls below a predetermined set value V _s, so as to prolong the duration of the half cycle of the low frequency current Configured ,
In the control circuit, when the high pressure discharge lamp voltage if that maintains more than a predetermined value V _t that is controlled to power applied to the high-pressure discharge lamp is constant, below the predetermined value V _t It is configured to be controlled so that the input current to the high pressure discharge lamp is constant,
The high pressure discharge lamp lighting device, wherein the predetermined set value V _s is equal to a predetermined value V _t-full for all-light lighting . In the high pressure discharge lamp lighting device according to claim 1,
When the duration of a half cycle of the low frequency current is lengthened, if {the high frequency 1 cycle + low frequency half cycle (negative) + high frequency 1 cycle + low frequency half cycle (positive)} is 1 cycle, the cycle is A high pressure discharge lamp lighting device, wherein the control circuit is configured to be 60 Hz to 100 Hz. The high pressure discharge lamp lighting device according to claim 1 or 2 , dimming signal oscillation means for generating the dimming signal, the cooling fan, the high pressure discharge lamp, a reflector to which the high pressure discharge lamp is attached, and at least the high pressure A light source device comprising a housing containing a discharge lamp lighting device.

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